Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.66	5.866%	$182.7882	$182.79	$182.80	$182.80
Purchase #2	$83.46	9.787%	$91.6282	$91.63	$91.65	$91.60
Purchase #3	$149.45	10.478%	$165.1094	$165.11	$165.10	$165.10
Purchase #4	$193.78	11.338%	$215.7508	$215.75	$215.75	$215.80
Purchase #5	$213.93	8.349%	$231.791	$231.79	$231.80	$231.80
Purchase #6	$84.36	6.172%	$89.5667	$89.57	$89.55	$89.60
Purchase #7	$83.71	7.330%	$89.8459	$89.85	$89.85	$89.80
7 purchase totals =	$981.35		$1,066.4802	$1,066.49	$1,066.50	$1,066.50